The 11/11 dupe, also known as the Jump Dupe, was a massive duplication glitch on the server that occurred on November, 11th, 2016. The easy way to duplicate items was leaked to the 2b2t community by RusherIsAutistic, causing mass duping across the entire server.
The dupe involved tossing an item out and instantly disconnecting the server. When you logged back in, your item on the ground and in your inventory, which sparked the mass-dupe. This was the largest duplication glitch that the server had ever seen before then since you could dupe your entire inventory at once.
On 11/19, a client by Kinorana made to make duping easier was spread among the community. You would be able to drop your entire inventory on the ground at once and automatically disconnect. You could now dupe your entire inventory at once. However, the client was actually backdoored, and people who duped using the client had their stashes leaked on the 2b2t Reddit.
However, a specific group of players, the 4th Reich, had another way to duplicate. This was the first method used before other client's were made consisting of other types of kicks that could be used. This method involved using two Minecraft windows which you would login to one and drop an item before being kicked on the other.
The 11/11 Dupe caused the amount of items in the server to overflow, with most players having double chests of God Apples and other rare items. This caused the 2b2t economy to crash,with items from the dupe still in mass circulation today.